1. Field of the Invention
The present invention relates to an apparatus for bending glass panes in a horizontal position, comprising a bending mold fixed, above the conveying plane of the glass panes, to vertical guide rods and arranged to be raised and lowered by these rods, the bending force of which is determined by the self-weight of the bending mold, and comprising at least one lower bending mold, capable of being horizontally traversed in the direction of conveying of the glass panes.
2. Description of the Related Art
Bending apparatuses of this type are known in various forms of construction. In one form of construction, a single, lower peripheral bending mold is provided, which can be traversed between a transfer station and the bending station (EP 0 183 418). In the transfer station, the glass pane, heated in a roller once-through furnace to bending temperature and lifted off the conveying rollers by a suction plate disposed above the conveying plane, is laid down on the lower peripheral bending mold, and the lower peripheral bending mold is then traversed, together with the glass pane, beneath the upper bending mold.
In another known apparatus of the initially named type, the glass panes are conveyed on a conveyor roller path into the bending station, in which the last portion of the conveyor roller path is lowered, the glass pane being laid down on a lower, peripheral bending mold. The upper bending mold then descends and carries out the pressing operation. The bent glass pane is then, together with the peripheral bending mold, withdrawn from the bending station, while at the same time a new peripheral bending mold is brought into the bending station (EP 0 062 814).
A further form of construction of an apparatus according to the above category is also known, wherein the plane glass panes are conveyed on peripheral bending molds through the heating furnace and are bent into their final shape in the bending station by means of the upper bending mold.
In all the bending apparatuses of this category, it is difficult to position the horizontally displaceable, lower peripheral bending mold underneath the upper bending mold sufficiently accurately for the upper bending mold to press on the glass pane during the pressing operation with uniform force along the entire periphery of the pane. With the known constructions it is, as a rule, unavoidable that at some positions the upper bending mold will press with a higher force than at other positions onto the glass pane supported by the peripheral bending mold, which can lead to indentations on the glass pane or indeed to local deformations of the peripheral bending molds.
It is also known and common to avoid local pressure points on the glass pane by fitting adjustable stops outside the periphery of the pane on the peripheral bending mold (EP 0 237 231). Consequently, however, the pressure force is fully transmitted to these local stops, so that the risk of deformation of the peripheral bending mold is further increased. Moreover, in this case it is not possible to apply a uniform pressure along the entire periphery of the glass pane, because the stops inevitably must be adjusted to a somewhat greater distance than the thickness of the glass panes.